Cannula

ABSTRACT

A method of cannulating vasculature includes inserting the vasculature through a first clamping surface of a cannula and rotating a second clamping surface of the cannula around the first clamping surface to move from an open position towards a closed position. Additionally, the method includes securing the vasculature between the first clamping surface and the second clamping surface.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 13/545,199, filed Jul. 10, 2012, the contents of which areincorporated herein by reference.

BACKGROUND

Related technical fields include cannulas and clamping methods,including cannulas and clamping methods for perfusing one or more organsor tissue to monitor, treat, sustain and/or restore the viability of theorgan(s) or tissue and/or for transporting and/or storing the organ(s)or tissue.

Various devices have been developed that couple the anatomy of an organbeing perfused to a machine or other equipment equipment such as thatdescribed in U.S. Pat. No. 7,824,848, the entire disclosure of which ishereby incorporated by reference. Such devices are typically referred toas perfusion clamps or simply cannulas. Although the term cannula ingeneral use has other meanings, the term cannula is used genericallythroughout this specification to refer to a clamp or other device thatprovides a connection through which fluid flow may be established.

A type of cannula as described in U.S. Pat. No. 5,728,115 to Westcott etal., which is hereby incorporated by reference, is shown in FIGS. 1-3. Aclamping device (cannula) 10 is used to couple a perfusion device to therenal aorta 34. The clamp 10 includes two longitudinal members 12 and 14which pivot about a pin 16. The proximal end of the member 12 includesan integral handle 18, while the proximal end of the member 14 includesan integral handle 20. The distal end of the member 12 includes anelongated, hollow, annular, integral clamp head 24, while the distal endof the member 14 includes an elongated, hollow, annular, integral clamphead 26. Clamp head 26 includes a nipple 28 attached thereto. Movementof the handles 18 and 20 toward one another forces the members 12 and 14to pivot about the pin 16, thereby forcing the clamp heads 24 and 26 ofthe members 12 and 14 away from one another. A spring 22 is positionedbetween the handles 18 and 20 in order to bias the handles apart. This,in turn, tends to force the clamp heads 24 and 26 together. Therefore,the clamp heads 24 and 26 of the distal ends of the members 12 and 14are engaged in a clamping relationship unless an external compressiveforce is applied to the handles 18 and 20. A lumen 32 extends throughthe nipple 28.

In use, the clamp 10 is attached to a blood vessel of a donor organ suchas the renal aorta 34 of a kidney 36 by opening the clamp 10, passingthe distal end 38 of the renal aorta 34 through the annular clamp head24, holding the distal end 38 of the renal aorta 34 over the annularclamp head 24, and releasing pressure on the handles of the clamp 10 inorder to allow the clamp head 26 to engage the distal end 38 of therenal aorta 34 against the annular clamp head 24. A catheter 40 may thenbe attached to the nipple 28 in order to provide perfusion of liquidthrough the lumen 32 and into the renal aorta 34.

SUMMARY

The cannula as described above is difficult and/or cumbersome to usebecause the spring 22 biases the clamp heads 24 and 26 together. Theproblem is at least two-fold. First, a user must actively hold open thecannula 10 in order to insert the renal aorta into the clamp head 24.This leaves one hand available for the user to manipulate the renalaorta or requires the help of a second user. Also, this configurationresults in a force being applied by default, and that force is notadjustable because it is determined by the spring constant and thethickness of any clamped tissue (neither of which is adjustable by auser). Second, the clamp head 24 obscures the user's view of andrestricts access to the clamp head 26, in particular the interiorpassage and clamping surface.

The cannula as described above also is cumbersome because it includeshandles 18 and 20. The handles are necessary to open the cannula, butare otherwise extraneous. When used in conjunction with an organperfusion apparatus, the handles may be too large or in the way when theorgan is disposed in an organ perfusion apparatus, which could result indamage if the handles contact delicate tissue. The cannula describedabove also will engage any blood vessel between heads 24 and 26 in anuneven manner because the portion of the heads 24 and 26 nearest the pin16 will typically contact the blood vessel before portions of the heads24 and 26 further away from the pin 16. Such uneven engagement mayresult in an unequal distribution of force that may damage the bloodvessel. Also, the nipple 28 in the cannula as described above extendsperpendicular from the clamping surfaces. This configuration may becumbersome or unacceptable for use in tight spaces. The nipple 28 mayalso leak.

A cannula may include a first clamping surface on a closing portion ofthe cannula, a second clamping surface on a base of the cannula, and aconnecting structure that connects the closing portion and the base. Theconnecting structure may allow the closing portion to be rotated aroundthe second clamping surface. Preferably, the first clamping surface andthe second clamping surface are configured to secure tissue between thefirst clamping surface and the second clamping surface. The closingportion may preferably be rotatable at least 90°, preferably at least180° or 360° around the second clamping surface. When rotating aroundthe second clamping surface, the first clamping surface preferablyremains facing the base. Preferably, the closing portion is rotatableabout the base in the open position and the closing portion is notrotatable about the second clamping surface in the closed position.

The connecting structure may be configured to bias the closing portiontowards the base and to bias the closing portion away from the base.

The cannula preferably includes at least one passage in the closingportion and/or the base. Preferably, a passage in the closing portionprovides fluid communication between an opening in the first clampingsurface and another opening, which preferably provides an external fluidconnection, for example to perfusion apparatus. The passage in theclosing portion may be straight or may include a turn, and the passagemay change size and/or shape to transition from the opening in the firstclamping surface to the other opening. Preferably, a passage in the baseconnects an opening in the second clamping surface and a second openingin the base, which in combination allow for a free end of vasculature topass through the second opening and then through the opening in thesecond clamping surface.

Exemplary implementations may include a handle that can be repeatablyattached to and removed from the cannula. Preferably, the removablehandle has a length that is more than half of the overall length of thecannula. The removable handle may be attached in various ways, forexample by way of a releasable snap fit or by way of mating threads.Preferably, the cannula is fully functional for providing fluid flow toor from a cannulated vasculature with or without the handle. A removablehandle provides advantages. For example, cannulas may be small relativeto the size of a user's hands due to the size of the vasculature to becannulated. For example, vasculature can be on the order of about threeto seven millimeters in diameter. The resulting geometry for cannulatingsuch a vasculature can be quite small relative to a user's hands,resulting in difficulty manipulating such relatively small geometry. Byadding a handle, the cannula can be more easily manipulated by a user.However, the addition of a handle makes the cannula much larger, whichmay result in difficulties in use, where the handle may get in the wayof other devices (such as portions of an organ perfusion apparatus). Byincluding a removable handle, ease of use and/or manipulation can beimproved with the handle on the cannula while a relatively small sizecan be achieved with the handle removed.

Exemplary implementations include a method of cannulating vasculatureincluding inserting the vasculature through a hole in a cannula, foldingback a portion of the vasculature to expose an interior of thevasculature, engaging an external surface of the portion with a firstclamping surface of the cannula; and engaging an internal surface of theportion with a second clamping surface of the cannula. Preferably, theangle that the vasculature is folded back is approximately 135°.

Exemplary methods may include manipulating a cannula by gripping ahandle with a user's hand and moving at least one clamping surface withthe thumb on the same hand The thumb may engage a surface, such as atextured surface, to initiate the movement. Moving the clamping surfacemay include rotating the clamping surface around a second clampingsurface, moving the clamping surface towards the second clamping surfaceand/or moving the clamping surface away from the second clampingsurface. Such movement may occur before the cannula has been used toclamp vasculature or after the cannula has been unclamped from thevasculature. Exemplary methods may also include attaching a handle to acannula before clamping vasculature with the cannula, or removingvasculature from the cannula, and/or removing a handle from a cannulaonce vasculature is clamped to the cannula.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary implementations are described herein with reference to thefollowing figures wherein:

FIGS. 1-3 illustrate a cannula of the prior art;

FIG. 4 illustrates a cannula in a closed state;

FIG. 5 illustrates a cross section of a cannula in a closed state;

FIG. 6 illustrates a portion of a cannula;

FIG. 7 illustrates a cannula in a closed state with a handle removed;and

FIG. 8 illustrates a cross section of a cannula in a closed state.

DETAILED DESCRIPTION OF EMBODIMENTS

Preservation of organs by machine perfusion has been accomplished athypothermic temperatures with or without computer control withcrystalloid perfusates and without oxygenation. See, for example, U.S.Pat. Nos. 5,149,321, 5,395,314, 5,584,804, 5,709,654 and 5,752,929 andU.S. patent application Ser. No. 08/484,601 to Klatz et al., which arehereby incorporated by reference in their entireties.

Ideally organs would be procured in a manner that limits their warmischemia time to essentially zero. Unfortunately, in reality, manyorgans, especially from non-beating heart donors, are procured afterextended warm ischemia time periods (e.g., 45 minutes or more). Themachine perfusion of these organs at low temperature has demonstratedsignificant improvement (Transpl Int 1996 Daemen). Numerous controlcircuits and pumping configurations have been utilized to achieve thisobjective and to machine perfuse organs in general. See, for example,U.S. Pat. Nos. 5,338,662 and 5,494,822 to Sadri; U.S. Pat. No. 4,745,759to Bauer et al.; U.S. Pat. Nos. 5,217,860 and 5,472,876 to Fahy et al.;U.S. Pat. No. 5,051,352 to Martindale et al.; U.S. Pat. No. 3,995,444 toClark et al.; U.S. Pat. No. 4,629,686 to Gruenberg; U.S. Pat. Nos.3,738,914 and 3,892,628 to Thome et al.; U.S. Pat. Nos. 5,285,657 and5,476,763 to Bacchi et al.; U.S. Pat. No. 5,157,930 to McGhee et al.;and U.S. Pat. No. 5,141,847 to Sugimachi et al., which are herebyincorporated by reference in their entireties.

The cannulas and clamping methods described herein may be used inconjunction with apparatus and methods described in U.S. Pat. Nos.6,014,864, 6,183,019, 6,241,945 and 6,485,450 to Owen, which are herebyincorporated by reference in their entireties. While these apparatus andmethods are related to organ recovery and transplantation, the cannulasand clamping methods described herein may also be used in various othermedical procedures and with various other medical equipment whereclamping with fluid flow is desired. Thus, the cannulas and clampingmethods described herein are not limited to the applications describedbelow in conjunction with the exemplary implementations.

FIG. 4 shows a perfusion clamping apparatus or cannula 100 according toa first exemplary implementation. The cannula 100 is capable ofconnecting one or more blood vessels of an organ or tissue to aperfusion machine or system (not shown), for example, by connection totubing of the perfusion machine or system. All medical fluid contactsurfaces are preferably formed of or coated with materials compatiblewith the medical fluid used, preferably non-thrombogenic materials. Forconvenience, the term “organ” will be used herein to mean organ and/ortissue, except as otherwise specified.

The medical fluid for perfusion may be any suitable medical fluid. Forexample, it may be a simple crystalloid solution, or may be augmentedwith an appropriate oxygen carrier. The oxygen carrier may, for example,be washed, stabilized red blood cells, cross-linked hemoglobin,pegolated hemoglobin or fluorocarbon based emulsions. The medical fluidmay also contain antioxidants known to reduce peroxidation or freeradical damage in the physiological environment and specific agentsknown to aid in tissue protection. Further, the medical fluid may be orinclude blood or blood products.

A cannula 100 as described herein may be used in various advantageousways. The cannula 100 may advantageously be manipulated with a singlehand of a user. The user may grip the handle 140 with one hand andmanipulate the closing portion 110 with a thumb on that same hand, whichmay rotate the closing portion 110 towards or away from an opened orclosed state. The user may advantageously attach the handle 140 if, forexample, the handle 140 is needed to grip the cannula 100 or the usermay remove the handle 140 if, for example, space constraints do notallow the cannula 100 to fit the space available with the handle 140attached. After the handle 140 has been removed, it may later beattached again. The handle 140 may be repeatably attached or removed forany reason.

The cannula 100 may be opened or closed such that the first clampingsurface 112 and the second clamping surface 122 are moved together orapart while the clamping surfaces remain parallel or nearly parallel.This may be advantageous in that any clamping force can be evenlyapplied or removed to avoid damage to clamped tissue. Such movement canbe achieved with a single hand. For example, a user can grip the handle140 with one hand while pressing down on the closing portion 110 withthe thumb of the same hand. Alternatively, while the handle is grippedin one hand, the user can move the first clamping surface 112 away fromthe second clamping surface 122 by inserting the user's thumb under theclosing portion to lift the closing portion 110.

The cannula 100 can be attached to an external fluid conduit.Preferably, the cannula 100 may be connected to an external fluidconduit after vasculature has been cannulated, but the cannula 100 maybe connected to an external fluid conduit prior to cannulation as well.Connection to an external fluid conduit may be achieved by connectingthe fluid conduit to a nipple 136. An external fluid conduit may providefluid communication for any use. For example, the external fluid conduitmay provide a connection between the cannula 100 and an organ perfusionmachine.

The cannula 100 shown in FIG. 4 and FIG. 5 is in a closed condition. Ina closed condition, a first clamping surface 112 on the closing portion110 and a second clamping surface 122 on the base 120 are in closeproximity to or in contact with one another. Preferably, in the closedcondition, the first clamping surface 112 and the second clampingsurface 122 may provide a gap between the surfaces to accommodate tissuesuch as vasculature. The first clamping surface 112 and the secondclamping surface 122 may be made from relatively soft (such aselastomeric) material or relatively hard material (such as plastics ormetal). Furthermore, one or both of the first clamping surface 112 andthe second clamping surface 122 may include ridges or a stair step-likestructure, which may help to retain a clamped tissue or vasculature.

The base 120 may include a connecting structure 130 that connects theclosing portion 110 to the base 120. Preferably, the connectingstructure 130 allows the closing portion 110 and/or the first clampingsurface 112 to be rotated around the base 120 and/or the second clampingsurface. As shown in the figures, the connecting structure allows a full360 degrees of rotation. However, varying amounts of rotation arecontemplated by the broad inventive principles described herein. Forexample, the connecting structure 130 may allow 90 degrees of rotation,180 degrees of rotation, or any other amount of rotation from 0-360degrees as dictated by the needs of a user. Such movement can beachieved with one hand of a user. For example, the user can grip thehandle 140 in one hand while applying a rotational force on the closingportion 110 with the thumb on that same hand. The rotational force ispreferably applied when the closing portion is in an open position.

As shown, the first clamping surface 112 defines a face of the closingportion 110. As the closing portion 110 is rotated around the base 120,the face remains facing the base. However, additional structure could beprovided that allows the face to change orientation if desired by a userand still be within the broad inventive principles described herein.

As shown in FIG. 6, the connecting structure 130 may include a firstlobe 132 and a second lobe 134. Together, these lobes form anapproximately figure-eight shape with a narrowing portion 133 betweenthe lobes. When interacting with an axle 124 (as shown at least in FIG.5), the lobes act to bias or hold the closing portion 110 towards oraway from the base 120 depending on the location of the axle 124 withrespect to the lobes. If the axle 124 is beyond an inflection point suchthat more of the axle 124 is within the first lobe 132 than the secondlobe 134, the base will be biased towards a closed position, whereas ifthe axle 124 is beyond the inflection point such that more of the axle124 is within the second lobe 134 than the first lobe 132, the base willbe biased towards an open position. The biasing between lobes is due tothe narrowing portion 133. Depending on the relative size of the lobes132, 134 and the axle 124, a biasing force may or may not continue to beapplied in the closed and open positions. For example, if the diameterof the axle 124 is slightly larger than the inner diameter of one of thelobes 132, 134, then there will be at least a slight interference fitwhich will continue to bias the axle 124 to whatever position it iscurrently in. However, if the diameter of the axle 124 is smaller thanthe inner diameter of one of the lobes 132, 134, then there will be aloose fit such that the biasing force will cease at an intermediatepoint between the inflection point and the closed or open position. Bothlobes 132, 134 may have an interference fit, both lobes 132, 134 mayhave a loose fit, or there may be a combination of loose andinterference fit. The axle 124 can be shifted between the lobes 132, 134with one hand of the user. For example, while the user grips the handle140 in one hand, the thumb of the same hand can either press down orlift up the closing portion 110, which may result in the axle 124 movingfrom one lobe to another.

Additionally, the narrowing portion 133 may interact with an indentationor opening 125 of the axle 124 (as shown in FIG. 5) to maintain theclosing portion 110 in an intermediate position. If the closing portionis rotated 90 degrees from the closed position, one side of thenarrowing portion 133 may engage the opening 124. Doing so will tend tokeep the closing portion 110 rotated 90 degrees and between the biasedopen (second lobe 134) position and the biased closed (first lobe 132)position. Of course, more than one opening 125 may be included, or asingle opening 125 may be positioned, such that the closing portion 110is maintained in any rotational position. For example, the rotationalposition could correspond to 45 degrees, 60 degrees, 75 degrees or anyother angle, or combination of angles, as dictated by the needs of auser. The closing portion 110 can be placed in the intermediate positionusing a single hand. For example, the handle 140 can be gripped in auser's hand and the thumb on that hand can apply a rotational force tothe closing portion 110 to rotate the closing portion 110 around thebase 120 until the base 110 is rotated to the appropriate rotationalangle. Once at that angle, the user can adjust the position of theclosing portion 110 with the thumb such that the narrowing portion 133engages the opening 125 and the closing portion 110 is thus in theintermediate position.

As can be seen in FIG. 5, the first clamping surface 112 and the secondclamping surface 114 may be formed as complementary surfaces. Forexample, FIG. 5 illustrates the first clamping surface 112 as forming aninterior acute angle whereas the second clamping surface 122 isillustrated as an exterior acute angle. Alternatively, both of theclamping surfaces can be described as approximately frustoconicalsections. When the first clamping surface 112 and the second clampingsurface 122 are in a closed condition, the complementary nature of thesurfaces tends to prevent the closing portion 110 from being rotatablearound the base 120, but in the open position, the closing portion 110is freely rotatable. The first clamping surface 112 and the secondclamping surface 114 may be made from soft elastomers to reduce injuryand/or trauma to the cellular structure of a cannulated vasculature.

As illustrated in FIG. 5, the base 120 includes a passage 123 with twoopenings. One of the openings is shown as surrounded by the secondclamping surface 122 and the other opening is shown on a side of thebase 120 opposite from the second clamping surface 122. The passage 123is shown as having an approximately oval shaped cross section, but othershapes are contemplated in the broad inventive principles describedherein. For example, the passage 123 could have a circular crosssection. In use, the passage 123 provides a space through whichvasculature may pass to be clamped between the first clamping surface112 and the second clamping surface 122. Preferably, the vasculature isinserted through the passage 123 with a free end of the vasculature ator near the second clamping surface 122. Then, the vasculature can befolded back such that an internal surface of the vasculature is exposedand the internal surface can be contacted by the first clamping surface112 when the cannula 100 is in a closed position. Preferably, thevasculature is folded back more than 90 degrees and more preferablyapproximately 135 degrees. The amount that the vasculature is foldedback may be defined by an angle of the first clamping surface 112 and/orthe second clamping surface 122. For example, and angle of the secondclamping surface may be between 105 degrees and 150 degrees when definedbetween the second clamping surface 122 and an axis of the passage 123.Alternatively, the angle may be defined between an interior surface ofthe passage 123 and the clamping surface 122, which may be between 30degrees and 60 degrees. If the angle is approximately 135 degrees, thecontact area of the first clamping surface 112 and the second clampingsurface 114 may be maximized while maintaining an evenly distributedclamping force. In this context, approximately is intended to encompassstandard manufacturing tolerances for angles, but includes a toleranceof at least plus or minus ten degrees. The amount the vasculature isfolded back will generally be dictated by an angle formed by the firstclamping surface 112 and/or the second clamping surface 122.

FIG. 5 also illustrates a connection for tubing, such as a nipple 136.The nipple 136 includes part of an internal passage within the closingportion 110. The first clamping surface 112 approximately surrounds oneopening of the internal passage and a second opening of the internalpassage is at or near an end of the nipple 136. Although a nipple isillustrated in the figures, other connection types are contemplated bythe broad inventive principles described herein. For example, standardluer geometry or other suitable structure may be used instead of anipple.

As shown in FIG. 5, the internal passage of the closing portion 110changes diameter but is straight. However, the internal passage mayinclude an internal bend, such that the nipple 136 is at an angle to thefirst clamping surface 112. As shown in FIG. 8, the internal passage asit passes through the nipple 136 is at an angle of approximately 90degrees with respect to the internal passage of FIG. 5. With such abend, a surface defined by the opening at the end of the nipple 136 isapproximately perpendicular to the first clamping surface 112, whichresults in an axis of the opening at the end of the nipple 136 beingapproximately parallel an axis of rotation of the closing portion 110about the base 120. The axle 124 may define such an axis of rotation.Alternatively, the nipple 136 may be disposed on a side of the closingportion 110, resulting in a similar relative position between thesurface defined by the end of the nipple 136 and the first clampingsurface 112. Also, other configurations may result in other exemplaryangles between the end of the nipple 136 and the first clamping surface112 as dictated by the needs of a user or by the geometry of a devicewhere the cannula 100 is used. Exemplary angles may be, but are notlimited to, 15 degrees, 30 degrees, 45 degrees, 60 degrees or 75degrees.

As illustrated in FIG. 4, the cannula 100 may include a first latchingmember 150 and/or a second latching member 152. The first latchingmember 150 and the second latching member 152 may preferably be madefrom an elastomeric material, preferably with good tear resistance andcompression set properties, which may include medical grade siliconerubber or synthetic polyisoprene or equivalents. The latching membersinclude holes that mate with the protrusions 154. Alternatively, thepositions of the holes and protrusions may be reversed such that theprotrusions are on one or both of the latching members. The latchingmembers may include a series of holes that provide the ability to applyvaried clamping forces urging the closing portion 110 towards the base120. Two sets of holes are illustrated, which may allow for twodifferent clamping forces, but any number of holes or sets of holes arecontemplated in the broad inventive principles described herein. Thelatching members 150, 152 can preferably be disengaged with a singlehand of a user. For example, the user can grip the handle 140 in onehand and use the thumb on that hand to disengage one or both of thelatching members 150, 152. The user can insert their thumb between alatching member 150, 152 and the closing portion 110 and apply a forceto separate the latching member 150, 152 from the protrusions 154.Alternatively, the user can use both hands to manipulate the latchingmembers 150, 152. Preferably, the latching members 150, 152 can berepeatably actuated as desired by the user.

FIGS. 4 and 5 show a handle 140 disposed on the cannula 100. Preferably,the cannula 100 is fully functional for cannulating and/or providingflow to vasculature with and without the handle in place. FIG. 7 showsthe cannula 100 without the handle 140. Preferably, the handle 140 maybe provided such that the handle 140 can be repeatably attached to andremoved from the cannula 100. As described below, the handle shown inthe figures is attached by way of a releasable snap fit, but otherstructures are contemplated in the broad inventive principles describedherein. For example, the handle could be attached by way of mating maleand female threads or a frictional fit other than a snap fit.

As shown in FIGS. 4, 5 and 7, the handle 140 may be attached to thecannula 100 by way of a snap fit. FIG. 7 illustrates a protrusion 128that mates with an indentation or opening 142 (as shown in FIG. 4) whenthe insert 126 is inserted into the handle 140. The insert 126 may bemade flexible by way of the hollow portion 129 in the insert 126. Asshown in the figures, the hollow portion 129 is an approximatelyoval-shaped hole through the insert 126 but other shapes arecontemplated as well. The hollow portion 129 provides flexibility toallow the protrusion 128 to deflect when the insert 126 is inserted intoor removed from the handle 140. However, the broad inventive principlesdescribed herein encompass other ways in which a snap fit may be maderepeatably releasable, as would be understood by one of ordinary skill.

Each of the components of the cannula 100 can be made from any number ofmaterials based upon the broad inventive principles described herein.Some of the components may preferably made through injection molding ofplastic; however, other materials are contemplated as well.

The handle may be more than half of an overall length of the cannula100. Preferably, the handle is approximately three quarters of theoverall length of the cannula. For example, the handle maybe between 2and 6 inches long, preferably about 3 to 3.5 inches. However, any lengthof handle is within the broad inventive principles discussed herein.Preferably, the handle has an oval shaped cross section, but any shapecan be chosen based upon the needs of the user. If the handle has anoval shaped cross section, the minor diameter is preferablyapproximately 0.5-0.6 inches and the major diameter is preferableapproximately 0.5-0.7 inches. The handle may also include grippingfeatures that are shown as approximately oval shaped depressions and/orprotrusions, although other types of gripping features are contemplated.Preferably, the gripping features are about 0.05-0.2 inches, such asabout 0.1 inches high and/or deep. Including such gripping features isadvantageous because users are likely to use the cannula 100 whilewearing medical gloves, which can result in relatively low friction, andthe gripping features improve the user's ability to grip the cannula100.

The closing portion 110 may include ridges or other textures, preferablyon a side opposite the first clamping surface 112, for improved grippingor manipulation. For example, as show in FIG. 4, the closing portion 110may include several transverse ridges as well as one or morelongitudinal ridge on a handle side of the nipple 136. One or more ofthese ridges may allow a user to readily manipulate the position of theclosing portion 110 with a thumb of the hand gripping the handle 140.The user can grip the handle 140 in one hand and engage the ridges orother textures with the thumb of that hand. The ridges may be used inany of the one-handed manipulations discussed above.

While various features have been described in conjunction with theexamples outlined above, various alternatives, modifications,variations, and/or improvements of those features and/or examples may bepossible. Accordingly, the examples, as set forth above, are intended tobe illustrative. Various changes may be made without departing from thebroad spirit and scope of the underlying inventive principles.

What is claimed is:
 1. A method of cannulating vasculature, comprising:inserting the vasculature through a first clamping surface of a cannula;rotating a second clamping surface of the cannula around the firstclamping surface to move from an open position towards a closedposition; and securing the vasculature between the first clampingsurface and the second clamping surface.
 2. The method according toclaim 1, further including perfusing an organ or tissue through thesecured vasculature.
 3. The method according to claim 1, furtherincluding securing the cannula in the closed position with a latch. 4.The method according to claim 3, wherein the latch exerts a force urgingthe first clamping surface and the second clamping surface together whenin the closed position.
 5. The method according to claim 1, wherein thecannula includes a connecting structure that allows the second clampingsurface to rotate towards the closed position.
 6. The method accordingto claim 5, wherein the second clamping surface is attached to a baseand the connecting structure biases the second clamping surface towardand away from the base.
 7. The method according to claim 1, wherein thesecond clamping surface is rotatable 360°.
 8. The method according toclaim 1, further including attaching a handle to the cannula.
 9. Themethod according to claim 9, wherein the second clamping surface isrotatable about the handle in the open position and the second clampingsurface is not rotatable about the handle in the closed position. 10.The method according to claim 9, further including removing the handlefrom the cannula while the vasculature is clamped between the firstclamping surface and the second clamping surface.
 11. The methodaccording to claim 1, wherein a flow passage is defined through thefirst clamping surface and the second clamping surface when thevasculature is clamped.
 12. The method according to claim 11, wherein anangle defined between an interior surface of the flow passage and thefirst clamping surface is between 30° and 60°.
 13. The method accordingto claim 1, wherein securing the vasculature between the first clampingsurface and the second clamping surface includes folding back thevasculature around the first clamping surface.
 14. The method accordingto claim 1, wherein securing the vasculature between the first clampingsurface and the second clamping surface includes maintaining an evenlydistributed clamping force by the second clamping surface on thevasculature.
 15. A method of cannulating vasculature, comprising:inserting a free end of the vasculature through a hole in a cannula;folding back a portion of the vasculature at an angle more than 90° toexpose an interior of the vasculature; engaging an external surface ofthe portion with a first clamping surface of the cannula; and engagingan internal surface of the portion with a second clamping surface of thecannula to maintain the angle more than 90°.
 16. The method according toclaim 15, wherein the portion is a complete circumference of thevasculature.
 17. The method according to claim 15, wherein the angle ismaintained between 105° and 150°.
 18. The method according to claim 15,wherein the first clamping surface and the second clamping surfacetogether define the angle.
 19. The method according to claim 15, furtherincluding rotating the second clamping surface around the first clampingsurface to engage the internal surface of the portion with the secondclamping surface.
 20. The method according to claim 15, furtherincluding perfusing an organ or tissue through the vasculature.